Portable Power Supply

For some time now I have been looking to build a new power supply that was small, low cost portable and capable of operation away from mains power.
The desired capabilities are;-
Output Voltage 1.0 Volts to 25.0 Volts
Maximum current 1.0 Amps
Adjustment accuracy 0.1 Volts
Current limit adjustable 1.0 mA to 1.0 Amp
My challenge was to find a simple low cost way to set the output voltage since most digital pots are limited to around 5 Volts, it was not practical to use these.
I looked at many power supply regulators over the months to see if I could find a suitable regulator. Finally I found one that enabled me to change the reference voltage.
The reference voltage can be varied between 0 and 2.5 volts, and using this range with a 10:1 divider on the feedback gives the desired results.
The block diagram below shows the basis for the design.

PPS Block Diagram

Block Diagram of Power Supply

Screen Shot 2014-10-05 at 4.31.41 pm

Planned Display with Touchscreen


Posted in Projects, Test Equipment.

I'd like to hear your thoughts.